Seeding Solutions: Establishing Turfseed

However, at this time of year there are certain cultural practices that contractors should follow before, during and after seeding to improve stand establishment and, in turn, minimize weeds.

TIMING MATTERS. Late summer is the best time to seed cool-season grasses in the northern half of the country. The turf stand develops more quickly this time of year and weed pressure is at its lowest. Late summer seedings work because there is ample time and rainfall before the stand is exposed to next summer’s stresses. Seeding at any other time of year is less forgiving, and shortcuts taken during establishment will become visible and magnified during summer stress.

The next best time to seed is during winter. The trick is to prepare the soil and seed when soil temperatures are below 40 degrees Fahrenheit so the seed won’t germinate until the following spring. Generally, this dormant seeding should be done between Thanksgiving and Christmas, but can continue into March or April in some states.

Dormant seeding offers labor management and agronomic advantages. Contractors can schedule this work in late fall or winter when there is more scheduling flexibility and the seed can benefit from spring’s warming soil temperatures. Dormant seeding also eliminates the chance for delayed seeding due to wet weather.

However, avoid dormant seeding on areas prone to even mild erosion.

Even though dormant seeding Kentucky bluegrass in December can outperform spring seedings in April and May, there is some risk. A spring warm-up could initiate germination only to be followed by an extreme cold period that could kill seedlings. The risk of cold damage is greater with quick-germinating species like perennial ryegrass, so avoid dormant seeding this species. Dormant seeding is best for slow-germinating grass like Kentucky bluegrass.

BE PREPARED. Seedbed preparation can determine the success of stand establishment, which, in turn, determines the amount of weed pressure.

The first step is to clear the seedbed of large rocks, concrete, lumber and other objects that inhibit growth and establishment.

Uncompacted soil gives the turf a better chance of survival, so tilling a new seedbed prior to seeding is critical. After tilling, smooth the seedbed and allow it to settle through irrigation or rainfall. After settling, lightly rake the surface, and drop the seed at the recommended rate applied in at least two directions across the lawn. To maximize seed-to-soil contact on a new area, follow seeding with a light rolling.

To further help seedling development, apply a starter fertilizer in the seedbed at 1 to 1.5 pounds P2O5 per 1,000 square feet to provide phosphorus to young roots that can’t explore much soil volume.

Irrigation throughout summer is crucial. Irrigate lightly and frequently as soon as temperatures are warm enough for germination. Some companies provide extra sprinklers to the clients to ensure adequate irrigation.

A light layer of mulch or hydromulching will conserve moisture and speed establishment. A second application of starter fertilizer within four weeks of germination also is beneficial, as well as frequent fertilization with low rates of nitrogen every four weeks. The soil type and soil test recommendations determine exact fertilization needs.

While encouraging growth with fertilization, contractors also must tend to maintenance, such as mowing. Waiting too long to mow a new seeding is a common mistake. Mowing encourages lateral growth and increased density, so mow early and often after seeding. Plus, mowing will kill many of the tall-growing weeds that emerge in a new seeding. Therefore, start mowing as soon as the first few seedlings reach the desired mowing height.

CONTROLLING WEEDS EARLY ON. Some products can be used prior to seeding to effectively suppress annual weedy grasses like crabgrass. By far the most effective method is fumigation with methyl bromide, which kills weed seeds in the soil, as well as insects, nematodes and disease propagules. However, methyl bromide application requires specialized equipment that only a few companies offer, and it can be expensive and time-consuming in terms of area preparation. But for high-dollar areas that cannot risk weed problems, methyl bromide fumigation is still most effective.

Soil fumigants are gaining popularity in turf as the availability of methyl bromide decreases. These products can be effective when applied in the fall over an existing turf or when applied to a new turf and tilled in to kill all weed seeds. Consider this type of weed control in areas where perennial spreading weeds, such as bermudagrass, nimblewill or quackgrass, are likely.

Controlling dandelions, clover and other broadleaf weeds in spring seedings is not as important as controlling crabgrass because broadleaf weeds are usually not as aggressive as annual grassy weeds. Therefore, contractors can normally wait until September or October to use a postemergence product on broadleaf weeds. If control is desired before then, follow label instructions for the recommended application delay after seedling.

TO SEED OR NOT TO SEED. In some cases, seeding doesn’t make sense. Sod is much more durable and may be more practical when establishing a site in the summer. However, sod requires at least as much, if not more, soil preparation as seeding, and some contractors neglect this step. Poor soil preparation leads to poor sod performance and can increase the risk of patch diseases later in the life of the lawn. Using high-quality, fresh-cut sod from a reputable grower is also important.

In other cases, seeding a temporary turf like annual ryegrass is practical. Grade the sight and prepare the seedbed just as you would a permanent turf, then seed with annual ryegrass. Return in August, kill the annual ryegrass with a nonselective herbicide, rough up the surface to expose the soil and increase seed-soil contact, and then seed with the desired turf. This strategy can limit erosion during the summer, provide extra organic matter to the soil and allow soil to settle under the annual ryegrass undulations.

Late summer is still the best time to seed a lawn. For dormant seeding, optimize seed-to-soil contact and post-seeding care to increase the speed of establishment, thereby minimizing weed pressure. If herbicides are needed, there are a number of options depending on the target weed and the situation. Once an herbicide is chosen, refer to the label for specific use recommendations.